2-substituted disindenylmetallocenes, process for their preparation, and their use as catalysts in the polymerization of olefins

ABSTRACT

The novel metallocenes of the formula I                    
     in which, preferably, M 1  is Zr or Hf, R 1  and R 2  are alkyl or halogen, R 3  and R 4  are hydrogen, R 5  and R 6  are alkyl or haloalkyl, —(CR 8 R 9 ) m —R 7 —(CR 8 R 9 ) n — is a single- or multi-membered chain in which R 7  may also be a (substituted) hetero atom, and m+n is zero or 1, form, together with aluminoxanes as cocatalysts, a very effective catalyst system for the preparation of polyolefins of high molecular weight.

The present invention relates to novel 2-substituted bisindenylmetallocenes which can very advantageously be used as catalysts in the preparation of polyolefins of high molecular weight.

Polyolefins of high molecular weight are particularly important for the production of films, sheets or large hollow elements, such as, for example, tubes or moldings.

Chiral metallocenes are, in combination with aluminoxanes, active, stereospecific catalysts for the preparation of polyolefins (U.S. Pat. No. 4,769,510). These metallocenes also include substituted indene compounds. Thus, for example, the use of the ethylenebis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride/aluminoxane catalyst system is known for the preparation of isotactic polypropylene (cf. EP-A 185 918). Both this and numerous other polymerization processes coming under the prior art have, in particular, the disadvantage that, at industrially interesting polymerization temperatures, only polymers having an unacceptably low molecular weight are obtained.

Surprisingly, it has now been found that novel 2-substituted bisindenylmetallocenes are suitable catalysts for the preparation of olefin polymers of high isotacticity, narrow molecular weight distribution and high molecular weight.

The present invention therefore provides the compounds of the formula I below

in which

M¹ is a metal from group IVb, Vb or VIb of the Periodic Table,

R¹ and R² are identical or different and are a hydrogen atom, a C₁-C₁₀-alkyl group, a C₁-C₁₀-alkoxy group, a C₆-C₁₀-aryl group, a C₆-C₁₀-aryloxy group, a C₂-C₁₀-alkenyl group, a C₇-C₄₀-arylalkyl group, a C₇-C₄₀-alkyl-aryl group, a C₈-C₄₀-arylalkenyl group or a halogen atom,

R³ and R⁴ are identical or different and are a hydrogen atom, a halogen atom, a C₁-C₁₀-alkyl group, which may be halogenated, a C₆-C₁₀-aryl group, an —NR₂ ¹⁰, —SR¹⁰, —OSiR₃ ¹⁰, —SiR₃ ¹⁰ or —PR₂ ¹⁰ radical in which R¹⁰ is a halogen atom, a C₁-C₁₀-alkyl group or a C₆-C₁₀-aryl group,

R⁵ and R⁶ are identical or different and are as defined for R³ and R⁴, with the proviso that R⁵ and R⁶ are not hydrogen,

═BR¹¹, ═AlR¹¹, —Ge—, —Sn—, —O—, —S—, ═SO, ═SO₂, ═NR¹¹, ═CO, ═PR¹¹ or ═P(O)R¹¹, where

R¹¹, R¹² and R¹³ are identical or different and are a hydrogen atom, a halogen atom, a C₁-C₁₀-alkyl group, a C₁-C₁₀-fluoroalkyl group, a C₆-C₁₀-aryl group, a C₆-C₁₀-fluoroaryl group, a C₁-C₁₀-alkoxy group, a C₂-C₁₀-alkenyl group, a C₇-C₄₀-arylalkyl group, a C₈-C₄₀-arylalkenyl group or a C₇-C₄₀-alkylaryl group, or R¹¹ and R¹² or R¹¹ and R¹³, in each case with the atoms connecting them, form a ring,

M² is silicon, germanium or tin,

R⁸ and R⁹ are identical or different and are as defined for R¹¹, and

m and n are identical or different and are zero, 1 or 2, m plus n being zero, 1 or 2.

Alkyl is straight-chain or branched alkyl. Halogen (halogenated) is fluorine, chlorine, bromine or iodine, preferably fluorine or chlorine.

In the formula I, M¹ is a metal from group IVb, Vb or VIb of the Periodic Table, for example titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum or tungsten, preferably zirconium, hafnium or titanium.

R¹ and R² are identical or different and are a hydrogen atom, a C₁-C₁₀-, preferably C₁-C₃-alkyl group, a C₁-C₁₀-, preferably C₁-C₃-alkoxy group, a C₆-C₁₀-, preferably C₆-C₈-aryl group, a C₆-C₁₀-, preferably C₆-C₈-aryloxy group, a C₂-C₁₀-, preferably C₂-C₄-alkenyl group, a C₇-C₄₀-, preferably C₇-C₁₀-arylalkyl group, a C₇-C₄₀- , preferably C₇-C₁₂-alkylaryl group, a C₈-C₄₀-, preferably C₈-C₁₂-aryl alkenyl group or a halogen atom, preferably chlorine.

R³ and R⁴ are identical or different and are a hydrogen atom, a halogen atom, preferably a fluorine, chlorine or bromine atom, a C₁-C₁₀-, preferably C₁-C₄-alkyl group, which may be halogenated, a C₆-C₁₀-, preferably C₆-C₈-aryl group, an —NR₂ ¹⁰, —SR¹⁰, —OSiR₃ ¹⁰, —SiR₃ ¹⁰, or PR₂ ¹⁰ radical in whcih R¹⁰ is a halogen atom, preferably a chlorine atom, or a C₁-C₁₀-, preferably C₁-C₃-alkyl group or a C₆-C₁₀-, preferably C₆-C₈-aryl group. R³ and R⁴ are particularly preferably hydrogen.

R⁵ and R⁶ are identical or different, preferably identical, and are as defined for R³ and R⁴, with the proviso that R⁵ and R⁶ cannot be hydrogen. R⁵ and R⁶ are preferably (C₁-C₄)-alkyl, which may be halogenated, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl or trifluoromethyl, in particular methyl.

═BR¹¹, ═AlR¹¹, —Ge—, —Sn—, —O—, —S—, ═SO, ═SO₂, ═NR¹¹, ═CO, ═Pr¹¹ or ═P(O)R¹¹, where R¹¹, R¹² and R¹³ are identical or different and are a hydrogen atom, a halogen atom, a C₁-C₁₀-, preferably C₁-C₄-alkyl group, in particular a methyl group, a C₁-C₁₀-fluoroalkyl group, preferably a CF₃ group, a C₆-C₁₀-, preferably C₆-C₈-aryl group, a C₆-C₁₀-fluoroaryl group, preferably a pentafluorophenyl group, a C₁-C₁₀-, preferably C₁-C₄-alkoxy group, in particular a methoxy group, a C₂-C₁₀-, preferably C₂-C₄-alkenyl group, a C₇-C₄₀-, preferably C₇-C₁₀-arylalkyl group, a C₈-C₄₀-, preferably C₈-C₁₂-arylalkenyl group or a C₇-C₄₀-, preferably C₇-C₁₂-alkylaryl group, or R¹¹ and R¹² or R¹¹ and R¹³, in each case together with the atoms connecting them, form a ring.

M² is silicon, germanium or tin, preferably silicon or germanium.

R⁷ is preferably ═CR¹¹R¹², ═SiR¹¹R¹², ═GeR¹¹R¹², —O—, —S—, ═SO, ═PR¹¹ or ═P(O)R¹¹.

R⁸ and R⁹ are identical or different and are as defined as for R¹¹.

m and n are identical or different and are zero, 1 or 2, preferably zero or 1, where m plus n is zero, 1 or 2, preferably zero or 1.

The particularly preferred metallocenes are thus those in which, in the formula I, M¹ is Zr or Hf, R¹ and R² are identical or different and are methyl or chlorine, R³ and R⁴ are hydrogen, R⁵ and R⁶ are identical or different and are methyl, ethyl or trifluoromethyl, R⁷ is a

radical, and n plus m is zero or 1; in particular the compounds I listed in the working examples.

Of the compounds I mentioned in the working examples, rac-dimethylsilyl(2-methyl-1-indenyl)₂zirconium dichloride, rac-ethylene(2-methyl-1-indenyl)₂zirconium dichloride, rac-dimethylsilyl(2-methyl-1-indenyl)₂dimethylzirconium and rac-ethylene(2-methyl-1-indenyl)₂dimethylzirconium are particularly important.

The chiral metallocenes are employed as racemates for the preparation of highly isotactic poly-1-olefins. However, it is also possible to use the pure R- or S-form. These pure stereoisomeric forms allow the preparation of an optically active polymer. However, the meso form of the metallocenes should be separated off since the polymerization-active center (the metal atom) in these compounds is no longer chiral due to mirror symmetry at the central metal, and it is therefore not possible to produce a highly isotactic polymer. If the meso form is not separated off, atactic polymer is formed alongside isotactic polymers. For certain applications—soft moldings for example—this may be entirely desirable.

The principle of resolution of the stereoisomers is known.

The present invention furthermore provides a process for the preparation of the metallocenes I, which comprises reacting a compound of the formula II

where R³-R⁹, m and n are as described in the formula I, and M³ is an alkali metal, preferably lithium,

a) with a compound of the formula III

M¹X₄   (III)

in which M¹ is as defined in the formula I, and X is a halogen atom, preferably chlorine, or

b) with a compound of the formula IIIa

M¹X₄L₂   (IIIa)

in which M¹ and X are as defined above, and L is a donor ligand,

and, if desired, derivatizing the resultant reaction product.

Examples of suitable donor ligands are tetrahydrofuran, diethyl ether, dimethyl ether and the like, preferably tetrahydrofuran (THF).

The synthesis is carried out under a protective gas and in anhydrous solvents. In case a), the dried salt of the formula II is added to a suspension of the compound of the formula III in a solvent such as toluene, n-hexane, dichloromethane, ether, THF, n-pentane or benzene, preferably in dichloromethane or toluene. The reaction temperature is from −78° C. to 30° C., preferably from −40° C to 10° C. The reaction duration is from 0.25 to 24 hours, preferably from 1 to 4 hours.

In case b), a solution of the salt of the formula II in one of the abovementioned solvents is added to a solution or suspension of a compound of the formula IIIa in a solvent such as toluene, xylene, ether or THF, preferably THF. However, an alternative procedure is to simultaneously add both components dropwise to a solvent. This is the preferred procedure. The reaction temperature is from −40° C. to 100° C., preferably from 0° C. to 50° C., in particular from 10° C. to 35° C. The reaction duration is from 0.25 hour to 48 hours, preferably from 1 hour to 24 hours, in particular from 2 hours to 9 hours.

The halogen derivatives obtained in this way can be converted into the alkyl, aryl or alkenyl complexes by known standard methods.

The compounds of the formula II are synthesized by deprotonation. This reaction is known; cf. J. Am. Chem. Soc., 112 (1990) 2030-2031, ibid. 110 (1988) 6255-6256, ibid. 109 (1987), 6544-6545, J. Organomet. Chem., 322 (1987) 65-70, New. J. Chem. 14 (1990) 499-503 and the working examples.

The synthesis of the protonated forms of the compounds of these formulae has also been described, with the difference that they are not correspondingly substituted in the α- and β-positions (Bull. Soc. Chim., 1967, 2954). The bridging units required for their synthesis are generally commercially available, but the indenyl compounds required, by contrast, are not. Some literature references containing synthesis procedures are indicated; the procedure for indene derivatives which are not mentioned is analogous: J. Org. Chem., 49 (1984) 4226-4237, J. Chem. Soc., Perkin II, 1981, 403-408, J. Am. Chem. Soc., 106 (1984) 6702, J. Am. Chem. Soc., 65 (1943) 567, J. Med. Chem., 30 (1987) 1303-1308, Chem. Ber. 85 (1952) 78-85 and the working examples.

The metallocenes I can thus in principle be prepared in accordance with the reaction scheme below:

The cocatalyst used according to the invention in the polymerization of olefins is an aluminoxane of the formula (IV)

for the linear type and/or of the formula (V)

for the cyclic type, where, in the formulae (IV) and (V), the radicals R may be identical or different and are a C₁-C₆-alkyl group, a C₆-C₁₈-aryl group or hydrogen, and p is an integer from 2 to 50, preferably from 10 to 35.

The radicals R are preferably identical and are methyl, isobutyl, phenyl or benzyl, particularly preferably methyl.

If the radicals R are different, they are preferably methyl and hydrogen or alternatively methyl and isobutyl, from 0.01 to 40% (of the number of radicals R) being hydrogen or isobutyl.

The aluminoxane can be prepared in different ways by known processes. One of the methods is, for example, the reaction of an aluminum-hydrocarbon compound and/or a hydridoaluminum-hydrocarbon compound with water (gaseous, solid, liquid or bound—for example as water of crystallization) in an inert solvent (such as, for example, toluene). In order to prepare an aluminoxane containing different alkyl groups R, two different trialkylaluminum compounds (AlR₃+AlR′₃) in accordance with the desired composition are reacted with water (cf. S. Pasynkiewicz, Polyhedron 9 (1990) 429 and EP-A 302 424).

The precise structure of the aluminoxanes IV and V is not known.

Irrespective of the preparation method, a varying content of unreacted aluminum starting compound, in free form or as an adduct, is common to all the aluminoxane solutions.

It is possible to preactivate the metallocene I using an aluminoxane of the formula (IV) and/or (V) before use in the polymerization reaction. This considerably increases the polymerization activity and improves the particle morphology.

The preactivation of the transition-metal compound is carried out in solution. The metallocene is preferably dissolved in a solution of the aluminoxane in an inert hydrocarbon. Suitable inert hydrocarbons are aliphatic or aromatic hydrocarbons. Toluene is preferred.

The concentration of the aluminoxane in the solution is in the range from about 1% by weight up to the saturation limit, preferably from 5 to 30% by weight, in each case based on the entire solution. The metallocene can be employed in the same concentration, but is preferably employed in an amount of from 10⁻⁴-1 mol per mole of aluminoxane. The preactivation time is from 5 minutes to 60 hours, preferably from 5 to 60 minutes. The preactivation temperature is from −78° C. to 100° C., preferably from 0° to 70° C.

The metallocene can also be prepolymerized or applied to a support. The prepolymerization is preferably carried out using the olefin or one of the olefins employed in the polymerization.

Examples of suitable supports are silica gels, aluminum oxides, solid aluminoxane or other inorganic support materials. Another suitable support material is a polyolefin powder in finely divided form.

A further possible variation of the process comprises using a salt-like compound of the formula R_(x)NH_(4-x)BR′₄ or of the formula R₃PHBR′₄ as cocatalyst instead of or in addition to an aluminoxane. x here is 1, 2 or 3, the R radicals are identical or different and are alkyl or aryl, and R′ is aryl, which may also be fluorinated or partially fluorinated. In this case, the catalyst comprises the product of the reaction of a metallocene with one of said compounds (cf. EP-A 277 004).

The polymerization or copolymerization is carried out in a known manner in solution, in suspension or in the gas phase, continuously or batchwise, in one or more steps, at a temperature of from 0° to 150° C., preferably from 30° to 80° C. Olefins of the formula R^(a)—CH═CH—R^(b) are polymerized or copolymerized. In this formula, R^(a) and R^(b) are identical or different and are a hydrogen atom or an alkyl radical having 1 to 14 carbon atoms. However, R^(a) and R^(b), together with the carbon atoms connecting them, may also form a ring. Examples of such olefins are ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, norbornene or norbornadiene. In particular, propylene and ethylene are polymerized.

The molecular weight regulator added, if necessary, is hydrogen. The overall pressure in the polymerization system is from 0.5 to 100 bar. The polymerization is preferably carried out in the industrially particularly interesting pressure range of from 5 to 64 bar.

The metallocene is used in a concentration, based on the transition metal, of from 10⁻³ to 10⁻⁸, preferably from 10⁻⁴ to 10⁻⁷ mol of transition metal per dm³ of solvent or per dm³ of reactor volume. The aluminoxane is used in a concentration of from 10⁻⁵ to 10⁻¹ mol, preferably from 10⁻⁴ to 10⁻² mol, per dm³ of solvent or per dm³ of reactor volume. In principle, however, higher concentrations are also possible.

If the polymerization is carried out as a suspension or solution polymerization, an inert solvent which is customary for the Ziegler low-pressure process is used. For example, the polymerization is carried out in an aliphatic or cycloaliphatic hydrocarbon; examples of these which may be mentioned are butane, pentane, hexane, heptane, isooctane, cyclohexane and methylcyclohexane.

It is also possible to use a petroleum ether or hydrogenated diesel oil fraction. Toluene can also be used. The polymerization is preferably carried out in the liquid monomer.

If inert solvents are used, the monomers are metered in in gaseous or liquid form.

The polymerization can have any desired duration since the catalyst system to be used according to the invention exhibits only a low time-dependent drop in polymerization activity.

The process is distinguished by the fact that the metallocenes according to the invention give, in the industrially interesting temperature range of between 30° and 80° C., polymers of high molecular weight, high stereospecificity and good particle morphology.

The zirconocenes according to the invention, in particular, are in a molecular weight range which was the province of the hafnocenes in the previous prior art. However, the latter had the disadvantage of only low polymerization activity and very high catalyst costs, and the polymers prepared using them had poor powder morphology.

The examples below are intended to illustrate the invention in greater detail.

SYNTHESIS OF THE STARTING SUBSTANCES I) Synthesis of 2-Me-indene

110.45 g (0.836 mol) of 2-indanone were dissolved in 500 cm³ of diethyl ether, and 290 cm³ of 3 N (0.87 mol) ethereal methylGrignard solution were added dropwise at such a rate that the mixture refluxed gently. After the mixture had boiled for 2 hours under gentle reflux, it was transferred onto an ice/hydrochloric acid mixture, and a pH of 2-3 was established using ammonium chloride. The organic phase was separated off, washed with NaHCO₃ and sodium chloride solution and dried, giving 98 g of crude product (2-hydroxy-2-methylindane), which was not purified further.

This product was dissolved in 500 cm³ of toluene, 3 g of p-toluenesulfonic acid were added, and the mixture was heated on a water separator until the elimination of water was complete, and was evaporated, the residue was taken up in dichloromethane, the dichloromethane solution was filtered through silica gel, and the filtrate was distilled in vacuo (80° C./10 mbar). Yield: 28.49 g (0.22 mol/26%).

The synthesis of this compound is also described in: C. F. Koelsch, P. R. Johnson, J. Am. Chem. Soc., 65 (1943) 567-573.

II) Synthesis of (2-Me-indene)₂SiMe₂

13 g (100 mmol) of 2-Me-indene were dissolved in 400 cm³ of diethyl ether, and 62.5 cm³ of 1.6 N (100 mmol) n-butyllithium/n-hexane solution were added dropwise over the course of 1 hour with ice cooling, and the mixture was then stirred at ˜35° C. for a further 1 hour.

6.1 cm³ (50 mmol) of dimethyldichlorosilane were introduced into 50 cm³ of Et₂O, and the lithio salt solution was added dropwise at 0° C. over the course of 5 hours, the mixture was stirred overnight at room temperature and left to stand over the weekend.

The solid which had deposited was filtered off, and the filtrate was evaporated to dryness. The product was extracted using small portions of n-hexane, and the extracts were filtered and evaporated, giving 5.7 g (18.00 mmol) of white crystals. The mother liquor was evaporated, and the residue was then purified by column chromatography (n-hexane/H₂CCl₂ 9:1 by volume), giving a further 2.5 g (7.9 mmol/52%) of product (as an isomer mixture).

R_(f) (SiO₂; n-hexane/H₂CCl₂ 9:1 by volume)=0.37.

The ¹H-NMR spectrum exhibits the signals expected for an isomer mixture with respect to shift and integration ratio.

III) Synthesis of (2-Me-Ind)₂CH₂CH₂

3 g (23 mmol) of 2-Me-indene were dissolved in 50 cm³ of THF, 14.4 cm³ of 1.6 N (23.04 mmol) n-butyllithium/n-hexane solution were added dropwise, and the mixture was then stirred at 65° C. for 1 hour. 1 ml (11.5 mmol) of 1,2-dibromoethane was then added at −78° C., and the mixture was allowed to warm to room temperature and was stirred for 5 hours. The mixture was evaporated, and the residue was purified by column chromatography (SiO₂; n-hexane/H₂CCl₂ 9:1 by volume).

The fractions containing the product were combined and evaporated, the residue was taken up in dry ether, the solution was dried over MgSO₄ and filtered, and the solvent was stripped off.

Yield: 1.6 g (5.59 mmol/49%) of isomer mixture

R_(f) (SiO₂; n-hexane/H₂CCl₂ 9:1 by volume) =0.46.

The ¹H-NMR spectrum corresponds to expectations for an isomer mixture in signal shift and integration.

SYNTHESIS OF THE METALLOCENES I IV) Synthesis of rac-dimethylsilyl(2-Me-1-indenyl)₂-zirconium dichloride

1.68 g (5.31 mmol) of the chelate ligand dimethylsilyl (2-methylindene) were introduced into 50 cm³ of THF, and 6.63 cm³ of a 1.6 N (10.61 mmol) n-BuLi/n-hexane solution were added dropwise at ambient temperature over the course of 0.5 hour. The mixture was stirred for 2 hours at about 35° C., the solvent was stripped off in vacuo, and the residue was stirred with n-pentane, filtered off and dried.

The dilithio salt obtained in this way was added at −78° C. to a suspension of 1.24 g (5.32 mmol) of ZrCl⁴ in 50 cm³ of CH₂Cl₂, and the mixture was stirred at this temperature for 3 hours. The mixture was then warmed to room temperature overnight and evaporated. The ¹H-NMR spectrum showed, in addition to the presence of some ZrCl₄(thf)₂, a rac/meso mixture. After stirring with n-pentane and drying, the solid, yellow residue was suspended in THF, filtered off and examined by NMR spectroscopy. These three working steps were repeated a number of times; finally, 0.35 g (0.73 mmol/14%) of product was obtained in which the rac form, according to ¹H-NMR, was enriched to more than 17:1.

The compound exhibited a correct elemental analysis and the following NMR signals (CDCl₃, 100 MHz): δ=1.25 (s, 6H, Si-Me); 2.18 (s, 6H, 2-Me); 6.8 (s, 2H, 3-H-Ind); 6.92-7.75 (m, 8H, 4-7-H-Ind).

V) rac-Dimethylsilyl-(2-Me-l-indenyl)₂dimethyl zirconium

0.24 g (0.58 mmol) of rac-dimethylsilyl(2-Me-1-indenyl)₂zirconium dichloride in 40 cm³ of Et₂O was added dropwise at −50° C. with 1.3 cm³ of a 1.6 N (2.08 mmol) ethereal MeLi solution, and the mixture was stirred at −10° C. for 2 hours. The solvent was replaced by n-pentane, the mixture was stirred at room temperature for a further 1.5 hours, and the filtered residue was sublimed in vacuo, giving 0.19 g (0.44 mmol/81%) of sublimate having a correct elemental analysis.

VI) rac-Ethylene(2-Me-1-indenyl)₂zirconium dichloride

14.2 cm³ of 2.5 N (35.4 mmol) n-BuLi/n-hexane solution were added dropwise over the course of 1 hour at room temperature to 5.07 g (17.7 mmol) of the ligand ethylene (2-methylindene)₂ in 200 cm³ of THF, and the mixture was then stirred at about 50° C. for 3 hours. A precipitate which formed temporarily dissolved again. The mixture was left to stand overnight.

6.68 g (17.7 mmol) of ZrCl₄(thf)₂ in 250 cm³ of THF were added dropwise, simultaneously with the above dilithio salt solution, to about 50 cm³ of THF at 50° C., and the mixture was then stirred at this temperature for 20 hours. The toluene extract of the evaporation residue was evaporated. The residue was extracted with a little THF, and the product was recrystallized from toluene, giving 0.44 g (0.99 mmol/5.6%) of product in which the rac form was enriched to more than 15:1.

The compound exhibited a correct elemental analysis and the following NMR signals (CDCl₃, 100 MHz): δ=2.08 (2s, 6H, 2-Me); 3.45-4.18 (m, 4H, —CH₂CH₂—) ; 6.65 (2H, 3-H-Ind); 7.05-7.85 (m, 8H, 4-7-H-Ind).

VII) Me₂Zr[(2-Me-Ind)₂CH₂CH₂]

1.43 g (3.20 mmol) of Cl₂Zr[(2-Me-Ind) ₂CH₂CH₂] were dissolved in 50 cm³ of Et₂O, and 6 cm³ of 1.6 N (9.6 mmol) ethereal methyllithium solution were added dropwise at −40° C. The mixture was stirred at −10° C. for 2 hours and evaporated, the residue was taken up in n-hexane, the solution was stirred at room temperature for 1 hour, filtered and evaporated, and the product was sublimed.

Yield: 1.20 g (2.96 mmol/92%); correct elemental analysis.

VIII) Cl₂Zr[(2-Me-Ind)₂SiPh₂]

12.5 cm³ of 1.6 N (20 mmol) n-butyllithium/n-hexane solution were added dropwise over the course of 0.5 hour at room temperature to 4.41 g (10 mmol) of (2-Me-Ind) ₂SiPh₂ in 40 cm³ of THF, and the mixture was then stirred at 55° C. for 1 hour. The solvent was stripped off, and the residue was stirred in n-hexane, filtered off and dried in vacuo.

2.33 g (10 mmol) of ZrCl₄ were suspended in 50 cm³ of H₂CCl₂, the dilithio salt from the above reaction was added at −78° C., and the mixture was warmed to room temperature overnight. The mixture was filtered and evaporated, and the residue was washed with several small portions of THF and then dried in vacuo, giving 2.11 g (3.51 mmol/35%) of product. The elemental analysis corresponded to the C, H, Cl values required.

IX) Cl₂Zr[(2-Me-Ind)₂SiMePh]

12 cm³ of 2.5 N (30 mmol) n-butyllithium/n-hexane solution were added dropwise over the course of 1 hour at 10° C. to 5.68 g (15 mmol) of (2-Me-Ind)₂SiMePh in 50 cm³ of THF, and the mixture was then stirred at 50° C. for 1 hour and evaporated. The residue was suspended in n-hexane, filtered off and dried in vacuo.

3.5 g (15.02 mmol) of ZrCl₄ were suspended in 100 cm³ of H₂CCl₂, and the dilithio salt was added at −78° C. The mixture was then stirred at −25° C. for 6 hours and at 0° C. for 2 hours and then filtered. The filtrate was evaporated, and the residue was extracted a number of times with a little THF and then dried in vacuo.

Yield: 1.47 g (2.73 mmol/18%); with correct elemental analysis.

X) Cl₂Zr[(2-Et-Ind)₂CH₂CH₂]

9.6 cm³ of 2.5 N (24 mmol) n-butyllithium/n-hexane solution were added dropwise over the course of 10 minutes at room temperature to 3.77 g (11.99 mmol) of (2-Et-Ind)₂CH₂CH₂ in 150 cm³ of THF. The mixture was stirred at 50° C. for 2 hours, and the resultant dilithio salt solution was cooled to ambient temperature and added dropwise over the course of 6 hours at 35° C., simultaneously with an equal-volume solution of 4.53 g (12 mmol) of ZrCl₄, to 50 cm³ of THF, and stirring was continued overnight. The evaporated batch was extracted with several portions of a toluene/n-hexane mixture (3:1 by volume), and the extracts were filtered and evaporated. The residue was washed with small portions of THF and dried in vacuo.

Yield: 2.37 g (4.99 mmol/42%). The elemental analysis was correct.

XI) Cl₂Zr[(2-Et-Ind)₂SiMe₂]

22 5 cm³ of 1.6 N (36 mmol) ethereal methyllithium solution were added dropwise over the course of 1 hour at room temperature to 6.2 g (18 mmol) of (2-Et-Ind)₂SiMe₂ in 150 cm³ of THF, and the mixture was stirred at 45° C. until the evolution of gas was complete. The solvent was stripped off, and the residue was then digested in n-pentane, filtered off and dried in vacuo.

The dilithio salt was added at −45° C. to 4.2 g (18.02 mmol) of ZrCl₄ suspended in 100 cm³ of H₂CCl₂, and the mixture was allowed to warm to −20° C. The mixture was stirred at this temperature for 3 hours, warmed to room temperature, filtered and evaporated. The residue was then extracted with several portions of toluene, and the extracts were filtered and evaporated. The residue was stirred with n-hexane, filtered off and dried in vacuo.

Yield: 1.04 g (2.06 mmol/11%). The substance exhibited a correct elemental analysis.

XII) Cl₂Zr[(2-Me-Ind)₂CHMeCH₂]

8.85 cm³ of 1.6 N (14.16 mmol) n-butyllithium/n-hexane solution were added dropwise over the course of 0.5 hour at room temperature to 2.12 g (7.06 mmol) of (2-Me-Ind)₂CHMeCH₂ in 40 cm³ of THF, and the mixture was then stirred at 55° C. for 1.5 hours. This solution was then added at 0° C. over a period of 2 hours to 2.66 g (7.05 mmol) of ZrCl₄(thf)₂ in 50 cm³ of THF. The mixture was stirred at room temperature for 2 hours and evaporated, the residue was extracted with several small portions of toluene/n-hexane 1:1 (by volume), the extracts were evaporated, the residue was extracted with warm n-hexane, the extracts were evaporated, and the residue was filtered off.

Yield: 0.44 g (0.96 mmol/14%); correct elemental analysis.

XIII) Cl₂Zr[(2-Me-Ind)₂CMe₂]

8.2 cm³ (13.12 mmol) of 1.6 N ethereal methyllithium solution were added dropwise at 0° C. to 1.97 g (6.56 mmol) of (2-Me-Ind)₂CMe₂dissolved in 60 cm³ of Et₂O, and the mixture was then refluxed for 2 hours and evaporated. The residue was stirred with n-hexane, separated off and dried in vacuo.

The dilithio salt obtained was added at −50° C. to a suspension of 1.53 g (6.57 mmol) of ZrCl₄ in 60 cm³ of H₂CCl₂, the mixture was stirred at −35° C. for 3 hours, warmed to room temperature and filtered, the residue was extracted with a few portions of toluene/n-hexane, the extracts were evaporated, the residue was stirred with n-pentane, and the solvent was stripped off in vacuo.

Yield: 0.81 g (1.76 mmol/27%); correct elemental analysis.

XIV) Me₂Zr[(2-Me-Ind)₂SiMePh]

6.5 cm³ of 1.6 N (10.4 mmol) ethereal methyllithium solution were added dropwise at −50° C. to 2.29 g (4.25 mmol) of Cl₂Zr[(2-Me-Ind)₂SiMePh] dissolved in 50 cm³ of Et₂O, and the mixture was stirred at −25° C. for 2.5 hours. The solvent was replaced by n-hexane, and the mixture was stirred at room temperature for a further 1 hour and filtered, the filtrate was concentrated somewhat and re-filtered, and the solvent was evaporated.

Yield: 1.58 g (3.17 mmol/75%); correct elemental analysis.

Abbreviations:

Me=methyl, Et=ethyl, Bu=butyl, Ph=phenyl, Ind=indenyl, THF=tetrahydrofuran, PP=polypropylene, PE=polyethylene.

METALLOCENES I AS CATALYSTS FOR THE POLYMERIZATION OF OLEFINS

The following abbreviations are used:

VN = viscosity number in cm³/g determined by M_(w) = weight average molecular weight gel permeation in g/mol chromatography M_(w)/M_(n) = molecular weight dispersity II = isotactic index (II = mm + ½ r), determined by ¹³C-NMR spectroscopy BD = polymer bulk density in g/dm³ MFI (230/5) = melt flow index in g/10 min, measured in accordance with DIN 53735

EXAMPLE 1

12 dm³ of liquid propylene were introduced into a dry 24 dm³ reactor which had been flushed with nitrogen.

35 cm³ of a toluene solution of methylaluminoxane (corresponding to 52 mmol of Al, mean degree of oligomerization n=17) were then added, and the batch was stirred at 30° C. for 15 minutes.

In parallel, 6.9 mg (0.015 mmol) of rac-ethylene -(2-Me-1-Indenyl)zzirconium dichloride were dissolved in 13.5 cm³ of a toluene solution of methylaluminoxane (20 mmol of Al) and preactivated by standing for 15 minutes.

The solution was then introduced into the reactor and heated to 70° C. (10° C./min) by supply of heat, and the polymerization system was kept at 70° C for 1 hour by cooling. The polymerization was terminated by removing the excess monomer in gas form. 1.56 kg of polypropylene were obtained.

The activity of the metallocene was thus 226 kg of PP/g of metallocene×h.

VN=67 cm³/g; M_(w)=58 900 g/mol; M_(w)/M_(n)=2.0; II=95.9%;

BD=350 g/dm³.

EXAMPLE 2

Example 1 was repeated, but 10.1 mg (0.023 mmol) of the metallocene were used and the polymerization was carried out at 50° C.

0.51 kg of polymer powder were obtained, corresponding to a metallocene activity of 50.5 kg of PP/g of metallocene×h.

VN=100 cm³/g; M_(w)=108 500 g/mol; M_(w)/M_(n)=2.2; II=96.4%; MFI (230/5)=210 g/10 min.

EXAMPLE 3

Example 1 was repeated, but 10.5 mg (0.023 mmol) of the metallocene were employed and the polymerization was carried out at 30° C. for 10 hours.

1.05 kg of polymer powder were obtained, corresponding to a metallocene activity of 10.0 kg of PP/g of metallone ×h.

VN=124 cm³/g; M_(w)=157 000 g/mol; M_(w)/M_(n)=2.2; II=96.3%; MFI (230/5)=104 g/10 min.

COMPARATIVE EXAMPLES A-C

The polymerization was carried out in an analogous manner to Examples 1 to 3 using the metallocene rac-ethylenebisindenylzirconium dichloride. The viscosity numbers and molecular weights of the resultant polymer products were:

Polym. temp. VN M_(w) Comp. Ex. [° C.] [cm³/g] [g/mol] A 70 30 19 900 B 50 46 38 500 C 30 60 48 700

These comparative examples demonstrate the molecular weight-increasing effect of the substituent in the 2-position on the indenyl ligand.

EXAMPLE 4

The procedure was as in Example 1, but 4.0 mg (0.008 mmol) of rac-dimethylsilyl(2-methyl-1-indenyl)₂-zirconium dichloride were used.

The metallocene activity was 293 kg of PP/g of metallocene ×h.

VN=171 cm³/g; M_(w)=197 000 g/mol; M_(w)/M_(n=)2.5; II=96.0%; MFI (230/5)=43.2 g/10 min; BD=460 g/dm³; m.p.=145° C.

EXAMPLE 5

The procedure was as in Example 1, but 6.0 mg (0.013 mmol) of rac-dimethylsilyl(2-methyl-1-indenyl)₂-zirconium dichloride were used.

The polymerization temperature was 60° C. and the polymerization time was 1 hour.

The metallocene activity was 178 kg of PP/g of metallocene ×h.

VN=217 cm³/g; M_(w)=297 000 g/mol; M_(w)/M_(n)=2.3; II=96.4%; MFI (230/5)=12.9 g/10 min; m.p.=148° C.

EXAMPLE 6

The procedure was as in Example 1, but 2.4 mg (0.0052 mmol) of rac-dimethylsilyl(2-methyl-1-indenyl)₂-zirconium dichloride were used. The polymerization temperature was 50° C. and the polymerization time was 3 hours.

The metallocene activity was 89 kg of PP/g of metallocene ×h.

VN=259 cm³/g; M_(w)=342 500 g/mol; M_(w)/M_(n)=2.1; II=96.8%; MFI (230/5)=8.1 g/10 min; m.p.=150° C.

EXAMPLE 7

The procedure was as in Example 1, but 9.9 mg (0.021 mmol) of rac-dimethylsilyl(2-methyl -1-indenyl)₂-zirconium dichloride were used.

The polymerization temperature was 30° C. and the polymerization time was 2 hours.

The metallocene activity was 26.5 kg of PP/g of metallocene ×h.

VN=340 cm³/g; M_(w)=457 000 g/mol; M_(w)/M_(n)=2.4; II=96.0%; MFI (230/5)=2.5 g/10 min.

EXAMPLE 8

6 dm³ of a gasoline fraction having a boiling range of 100°-120° C. with the aromatic components removed, and 6 dm³ of liquid propylene were introduced into a dry 24 dm³ reactor which had been flushed with nitrogen. 35 cm³ of a toluene solution of methylaluminoxane (corresponding to 52 mmol of Al, mean degree of oligomerization n=17) were then added, and the batch was stirred at 30° C. for 30 minutes.

In parallel, 14.7 mg (0.031 mmol) of rac-dimethylsilyl (2-methyl-1-indenyl)zzirconium dichloride were dissolved in 13.5 cm³ of a toluene solution of methylaluminoxane (20 mmol of Al) and preactivated by standing for 30 minutes.

The solution was then introduced into the reactor, the polymerization system was kept at 50° C. for 1 hour by cooling. The polymerization was terminated by addition of 50 cm³ of isopropanol.

The metallocene activity was 159.2 kg of PP/g of metallocene ×h.

VN=188 cm³/g; M_(w)=240 000 g/mol; M_(w)/M_(n)=2.1; II=96.0%; MFI (230/5)=28.6 g/10 min.

EXAMPLE 9

Example 8 was repeated, but 15.2 mg (0.032 mmol) of the metallocene were used, the polymerization time was 2 hours, and the polymerization temperature was 30° C.

The metallocene activity was 24.1 kg of PP/g of metallocene ×h.

VN=309 cm³/g; M_(w)=409 000 g/mol; M_(w)/M_(n)=2.3; II=97.0%; MFI (230/5)=3.5 g/10 min.

COMPARATIVE EXAMPLES D-F

The polymerization was carried out in an analogous manner to Examples 4, 6 and 7 using the metallocene dimethylsilylbisindenylzirconium dichloride. The viscosity numbers and molecular weights of the resultant polymer products were:

Polym. temp. VN M_(w) Comp. Ex. [° C.] [cm³/g] [g/mol] D 70 47 37 500 E 50 60 56 000 F 30 77 76 900

These examples demonstrate the molecular weight-increasing effect of the substituent in the 2-position on the indenyl ligand.

EXAMPLE 10

Example 1 was repeated, but 4.1 mg (0.008 mmol) of the metallocene rac-phenyl(methyl)silyl(2-methyl-1-indenyl)₂-ZrCl₂ were used.

1.10 kg of polypropylene were obtained, corresponding to a metallocene activity of 269 kg of PP/g of metallocene ×h.

VN=202 cm³/g; M_(w)=230 000 g/mol; M_(w)/M_(n)=2.3; II=97%; MFI (230/5)=36 g/10 min; m.p.=147° C.

EXAMPLE 11

Example 1 was repeated, but 5.2 mg (0.009 mmol) of the metallocene rac-diphenylsilyl(2-methyl-1-indenyl)₂ZrCl₂ were used.

1.14 kg of polypropylene were obtained. The metallocene activity was thus 219 kg of PP/g of metallocene×h.

VN=298 cm³g; M_(w)=367 000 g/mol; M_(w)M_(n)=2.2; MFI (230/5)=7.1 g/10 min.

EXAMPLE 12

Example 1 was repeated, but 17.4 mg (0.038 mmol) of the metallocene rac-methylethylene(2-methyl-1-indenyl)₂ZrCl₂ were used.

2.89 kg of polypropylene were obtained. The metallocene activity was thus 165.9 kg of PP/g of metallocene×h.

VN=138 cm³/g; M_(w)=129 000 g/mol; M_(w)/M_(n)=2.2; m.p.=150° C.

EXAMPLE 13

Example 1 was repeated, but 9.6 mg (0.02 mmol) of the metallocene rac-dimethylsilyl(2-ethyl-1-indenyl)₂-zirconium dichloride were used.

1.68 kg of polypropylene, corresponding to a metallocene activity of 175.0 kg of PP/g of metallocene×h, were obtained.

VN=143 cm³/g; M_(w)=132 000 g/mol; M_(w)/M_(n)=2.3; m.p.=140° C. 

We claim:
 1. A compound of the formula I

in which M¹ is a metal from group IVb, Vb or VIb of the Periodic Table, R¹ and R² are identical or different and are a hydrogen atom, a C₁-C₁₀-alkyl group, a C₁-C₁₀-alkoxy group, a C₆-C₁₀-aryl group, a C₆-C₁₀-aryloxy group, a C₂-C₁₀-alkenyl group, a C₇-C₄₀-arylalkyl group, a C₇-C₄₀-alkylaryl group, a C₈-C₄₀-arylalkenyl group or a halogen atom, R³ and R⁴ are identical or different and are a hydrogen atom, a halogen atom, a C₁-C₁₀-alkyl group, which is optionally halogenated, a C₆-C₁₀-aryl group, an —NR₂ ¹⁰, —SR¹⁰, —OSiR₂ ¹⁰. —SiR₃ ¹⁰ or —PR₂ ¹⁰ radical in which R¹⁰ is a halogen atom, a C₁-C₁₀-alkyl group or a C₆-C₁₀-aryl group, R⁵ and R⁶ are identical or different and are as defined for R³ and R⁴, with the proviso that R⁵ and R⁶ are not hydrogen,

═Br¹¹, ═AlR¹¹, —Ge—, —Sn—, —O—, —S—, ═SO, ═SO₂, ═NR¹¹, ═CO, ═PR¹¹ or ═P(O)R¹¹, where R¹¹, R¹² and R¹³ are identical or different and are a hydrogen atom, a halogen atom, a C₁-C₁₀-alkyl group, a C₁-C₁₀-fluoroalkyl group, a C₆-C₁₀-aryl group, a C₆-C₁₀-fluoroaryl group, a C₁-C₁₀-alkoxy group, a C₂-C₁₀-alkenyl group, a C₇-C₄₀-arylalkyl group, a C₈-C₄₀-arylalkenyl group or a C₇-C₄₀-alkylaryl group, or R¹¹ and R¹² or R¹¹ and R¹³, in each case with the atoms connecting them, form a ring, M² is silicon, germanium or tin, R⁸ and R⁹ are identical or different and are as defined for R¹¹, and m and n are identical or different and are zero, 1 or 2, m plus n being zero, 1 or 2 .
 2. A compound of the formula I as claimed in claim 1, wherein, in the formula I, M¹ is Zr or Hf, R¹ and R² are identical or different and are methyl or chlorine, R³ and R⁴ are hydrogen, R⁵ and R⁶ are identical or different and are methyl, ethyl or trifluoromethyl, R⁷ is a

radical, and n plus m is zero or 1 .
 3. A compound of the formula I as claimed in claim 1, wherein the compound is Rac selected from the group consisting of rac-dimethylsilyl(2-methyl -1-indenyl)₂zirconium dichloride, rac-ethylene-(2-methyl-1-indenyl)₂zirconium dichloride, rac-dimethylsilyl(2-methyl-1-indenyl)₂dimethylzirconium, rac-ethylene(2-methyl-1-indenyl)₂dimethylzirconium, rac-phenyl(methyl)silyl(2-methyl-1-indenyl)₂zirconium dichloride, rac-diphenylsilyl(2-methyl-1-indenyl)₂zirconium dichloride, rac-methylethylene(2-methyl-1-indenyl)₂zirconium dichloride, rac-dimethylsilyl (2-ethyl-1-indenyl)₂zirconium dichloride, rac-ethylene(2-ethyl-1-indenyl)₂zirconiumdichloride, rac-isopropylidene(2-methyl-1-indenyl)₂zirconium dichloride or rac-phenyl(methyl)silyl(2-methyl 1-indenyl)₂dimethyl zirconium.
 4. A process for the preparation of a compound of the formula I as claimed in claim 1, which comprises reacting a compound of the formula II

where R³-R⁹, m and n are as described in the formula I, and M³ is an alkali metal, a) with a compound of the formula III M¹X₄   (III) in which M¹ is as defined in the formula I, and X is a halogen atom, or b) with a compound of the formula IIIa M¹X₄L₂   (IIIa) in which M¹ and X are as defined above, and L is a donor ligand, and optionally derivatizing the resultant reaction product.
 5. A process for the preparation of a compound of the formula I as claimed in claim 4, wherein M³ is lithium.
 6. A process for the preparation of a compound of the formula I as claimed in claim 4, wherein X is chlorine.
 7. A catalyst composition which comprises: a compound of the formula I as claimed in claim 1 and an aluminoxane.
 8. A compound as claimed in claim 1, wherein M¹ is zirconium, hafnium or titanium.
 9. a A compound as claimed in calim claim 1, wherein R¹ and R² are identical or different and are a hydrogen atom, a C₁-C₃-alkyl group, a C₁-C₃-alkoxy group, a C₆-C₈-aryl group, a C₆-C₈-aryloxy group, a C₂-C₄-alkenyl group, a C₇-C₁₀-arylalkyl group, a C₇-C₁₂-alkylaryl group, a C₈-C₁₂-arylalkenyl group or chlorine.
 10. A compound as claimed in claim 1, wherien R³ and R⁴ are identical or different and are a hydrogen atom, a fluorine, chlorine or bromine atom, a C₁-C₄-alkyl group which may be halogenated, a C₆-C₈-aryl group, a —NR₂ ¹⁰, —SR¹⁰, —OSiR₃ ¹⁰, —SiR₃ ¹⁰ or —PR₂ ¹⁰ radical in which R¹⁰ is a chlorine atom, or a C₁-C₃ alkyl group or a C₆-C₈-aryl group.
 11. A compound as claimed in claim 1, wherein R³ and R⁴ are hydrogen.
 12. A compound as claimed in claim 1, wherein R⁵ and R⁶ are identical.
 13. A compound as claimed in claim 1, wherein R⁵ and R⁶ are (C₁-C₄)-alkyl, which may be halogenated with methyl.
 14. A compound as claimed in claim 1, wherein R¹¹, R¹² and R¹³ are identical or different and are a hydrogen atom, a halogen atom, a C₁-C₄-alkyl group, a CF₃ group, a C₆-C₈-aryl group, a pentafluorophenyl group, a C₁-C₄-alkoxy group a C₂-C₄-alkenyl group, a C₇-C₁₀-arylalkyl group, a C₈-C₁₂-arylalkenyl group and a C₇-C₁₂-alkylaryl group, or R¹¹ or R₁₂ or R¹¹ and R¹³, in each case together with the atoms connecting them, form a ring.
 15. A compound as claimed in claim 1, wherein M² is silicon or germanium.
 16. A compound as claimed in claim 1, wherein R⁷ is ═CR¹¹R¹², ═SiR¹¹R¹², ═GeR¹¹R¹², —O—, —S—, ═SO, ═PR¹¹ or ═P(O)R¹¹.
 17. A compound as claimed in claim 1, wherein m and n are identical or different and are zero or 1 .
 18. A compound as claimed in claim 1, wherein m plus n is zero or 1 .
 19. A compound as claimed in claim 1, wherein M¹ is Zr or Hf, R¹ and R² are identical or different and are methyl or chlorine, R³ and R⁴ are hydrogen, R⁵ and R⁶ are identical or different and are methyl, ethyl or trifluoromethyl, and n plus m is zero or 1 .
 20. A compound of the formula I

in which M ¹ is zirconium or titanium, R ¹ and R ² are identical or different and are a hydrogen atom, a C ₁ -C ₁₀-alkyl group, a C ₁ -C ₁₀-alkoxy group, a C ₆ -C ₁₀-aryl group, a C ₆ -C ₁₀-aryloxy group, a C ₂ -C ₁₀-alkenyl group, a C ₇ -C ₄₀-arylalkyl group, a C ₇ -C ₄₀-alkylaryl group, a C ₈ -C ₄₀-arylalkenyl group or a halogen atom, R ³ and R ⁴ are identical or different and are a hydrogen atom, a halogen atom, a C ₁ -C ₁₀-alkyl group, which is optionally halogenated, a C ₆ -C ₁₀-aryl group, an —NR ₂ ¹⁰ , —SR ¹⁰ , —OSiR ₃ ¹⁰ , —SiR ₃ ¹⁰ or —PR ₂ ¹⁰ radical in which R ¹⁰ is a halogen atom, a C ₁ -C ₁₀-alkyl group or a C ₆ -C ₁₀-aryl group, R ⁵ and R ⁶ are identical or different and are as defined for R ³ and R ⁴ , with the proviso that R ⁵ and R ⁶ are not hydrogen, R ⁷ is

 ═BR ¹¹ , ═AlR ¹¹ , —Ge—, —Sn—, —O—, —S—, ═SO,═SO ₂ , ═NR ¹¹ , ═CO, ═PR ¹¹ or ═P(O)R ¹¹ , where R ¹¹ , R ¹² and R ¹³ are identical or different and are a hydrogen atom, a halogen atom, a C ₁ -C ₁₀-alkyl group, a C ₁ -C ₁₀-fluoroalkyl group, a C ₆ -C ₁₀-aryl group, a C ₆ -C ₁₀-fluoroaryl group, a C ₁ -C ₁₀-alkoxy group, a C ₂ -C ₁₀-alkenyl group, a C ₇ -C ₄₀-arylalkyl group, a C ₈ -C ₄₀-arylalkenyl group or a C ₇-C₄₀-alkylaryl group, or R ¹¹ and R ¹² or R ¹¹ and R ¹³ , in each case with the atoms connecting them, form a ring, M ² is silicon, germanium or tin, R ⁸ and R ⁹ are identical or different and are as defined for R ¹¹ and m and n are identical or different are zero, 1 or 2, m plus n being zero, 1 or
 2. 21. The compound as claimed in claim 20, wherein M¹ is zirconium.
 22. A compound of the formula I

in which M ¹ is a metal from group IVb, Vb or VIb of the Periodic Table, R ¹ is a hydrogen atom, a C ₁ -C ₁₀-alkyl group, a C ₁ -C ₁₀-alkoxy group, a C ₆ -C ₁₀-aryl group, a C ₆ -C ₁₀-aryloxy group, a C ₂ -C ₁₀-alkenyl group, a C ₇ -C ₄₀-arylalkyl group, a C ₇ -C ₄₀-alkylaryl group or a C ₈ -C ₄₀-arylalkenyl group, R ² is a hydrogen atom, a C ₁ -C ₁₀-alkyl group, a C ₁ -C ₁₀-alkoxy group, a C ₆ -C ₁₀-aryl group, a C ₆ -C ₁₀-aryloxy group, a C ₂ -C ₁₀-alkenyl group, a C ₇ -C ₄₀-arylalkyl group, a C ₇ -C ₄₀-alkylaryl group, a C ₈ -C ₄₀-arylalkenyl group or a halogen group, R ³ and R ⁴ are identical or different and are a hydrogen atom, a halogen atom, a C ₁ -C ₁₀-alkyl group, which is optionally halogenated, a C ₆ -C ₁₀-aryl group, an —NR ₂ ¹⁰ , —SR ¹⁰ , —OSiR ₃ ¹⁰ , —SiR ₃ ¹⁰ or —PR ₂ ¹⁰ radical in which R ¹⁰ is a halogen atom, a C ₁ -C ₁₀-alkyl group or a C ₆ -C ₁₀-aryl group, R ⁵ and R ⁶ are identical or different and are as defined for R ³ and R ⁴ , with the proviso that R ⁵ and R ⁶ are not hydrogen, R ⁷ is

 ═BR ¹¹ , ═AlR ¹¹ , —Ge—, —Sn—, —O—, —S—, ═SO, SO ₂ , ═NR ¹¹ , ═CO, ═PR ¹¹ or ═P(O)R ¹¹ , where R ¹¹ , and R ¹³ are identical or different and are a hydrogen atom, a halogen atom, a C ₁ -C ₁₀-alkyl group, a C ₁ -C ₁₀-fluoroalkyl group, a C ₆ -C ₁₀-aryl group, a C ₆ -C ₁₀-fluoroaryl group, a C ₁ -C ₁₀-alkoxy group, a C ₂ -C ₁₀-alkenyl group, a C ₇ -C ₄₀-arylalkyl group, a C ₈ -C ₄₀-arylalkenyl group or a C ₇ -C ₄₀-alkylaryl group, R ¹² is a halogen atom, a C ₁ -C ₁₀-alkyl group, a C ₁ -C ₁₀-fluoroalkyl group, a C ₆ -C ₁₀-aryl group, a C ₆ -C ₁₀-fluoroaryl group, a C ₁ -C ₁₀-alkoxy group, a C ₂ -C ₁₀-alkenyl group, a C ₇ -C ₄₀-arylalkyl group, a C ₈ -C ₄₀-arylalkenyl group or a C ₇ -C ₄₀-alkylaryl group, or R ¹¹ and R ¹² or R ¹¹ and R ¹³ , in each case with the atoms connecting them, form a ring, M ² is silicon, germanium or tin, R ⁸ and R ⁹ are identical or different and are as defined for R ¹¹ and m and n are identical or different and are zero, 1 or 2, m plus n being zero, 1 or
 2. 23. A compound of the formula I

in which M ¹ is a metal from group IVb, Vb or VIb of the Periodic Table, R ¹ and R ² are identical or different and are a hydrogen atom, a C ₁ -C ₁₀-alkyl group, a C ₁ -C ₁₀-alkoxy group, a C ₆ -C ₁₀-aryl group, a C ₆ -C ₁₀-aryloxy group, a C ₂ -C ₁₀-alkenyl group, a C ₇ -C ₄₀-arylalkyl group, a C ₇ -C ₄₀-alkylaryl group, a C ₈ -C ₄₀-arylalkenyl group or a halogen atom, R ³ and R ⁴ are identical or different and are a hydrogen atom, a halogen atom, a C ₁ -C ₁₀-alkyl group, which is optionally halogenated, a C ₆ -C ₁₀-aryl group, an —NR ₂ ¹⁰ , —SR ¹⁰ , —OSiR ₃ ¹⁰ , —SiR ₃ ¹⁰ or —PR ₂ ¹⁰ radical in which R ¹⁰ is a halogen atom, a C ₁ -C ₁₀-alkyl group or a C ₆ -C ₁₀-aryl group, R ⁵ and R ⁶ are identical or different and are as defined for R ³ and R ⁴ , with the proviso that R ⁵ and R ⁶ are not hydrogen, R ⁷ is

 ═BR ¹¹ , ═AlR ¹¹ , —Ge—, —Sn—, —O—, —S—, ═SO,═SO ₂ , ═NR ¹¹ , ═CO, ═PR ¹¹ or ═P(O)R ¹¹ , where R ¹² is a halogen atom, a C ₁ -C ₁₀-alkyl group, a C ₁ -C ₁₀-fluoroalkyl group, a C ₆ -C ₁₀-aryl group, a C ₆ -C ₁₀-fluoroaryl group, a C ₁ -C ₁₀-alkoxy group, a C ₂ -C ₁₀-alkenyl group, a C ₇ -C ₄₀-arylalkyl group, a C ₈ -C ₄₀-arylalkenyl group or a C ₇ -C ₄₀-alkylaryl group, R ¹¹ and R ¹³ are identical or different and are a hydrogen atom, a halogen atom, a C ₁ -C ₁₀-alkyl group, a C ₁ -C ₁₀-fluoroalkyl group, a C ₆ -C ₁₀-aryl group, a C ₆ -C ₁₀-fluoroaryl group, a C ₁ -C ₁₀-alkoxy group, a C ₂ -C ₁₀-alkenyl group, a C ₇ -C ₄₀-arylalkyl group, a C ₈ -C ₄₀-arylalkenyl group or a C ₇ -C ₄₀-alkylaryl group, or R ¹¹ and R ¹² or R ¹¹ and R ¹³ , in each case with the atoms connecting them, form a ring, M ² is silicon, germanium or tin, R ⁸ and R ⁹ are identical or different and are as defined for R ¹¹ and m and n are identical or different and are zero, 1 or 2, m plus n being zero, 1 or
 2. 24. A compound of the formula I

in which M ¹ is a metal from group IVb, Vb or VIb of the Periodic Table, R ¹ and R ² are identical or different and are a hydrogen atom, a C ₁ -C ₁₀-alkyl group, a C ₁ -C ₁₀-alkoxy group, a C ₆ -C ₁₀-aryl group, a C ₆ -C ₁₀-aryloxy group, a C ₂ -C ₁₀-alkenyl group, a C ₇ -C ₄₀-arylalkyl group, a C ₇ -C ₄₀-alkylaryl group, a C ₈ -C ₄₀-arylalkenyl group or a halogen atom, R ³ and R ⁴ are identical or different and are a hydrogen atom, a halogen atom, a C ₁ -C ₁₀-alkyl group, which is optionally halogenated, a C ₆ -C ₁₀-aryl group, an —NR ₂ ¹⁰ , —SR ¹⁰ , —OSiR ₃ ¹⁰ , —SiR ₃ ¹⁰ or —PR ₂ ¹⁰ radical in which R ¹⁰ is a halogen atom, a C ₁ -C ₁₀-alkyl group or a C ₆ -C ₁₀-aryl group, R ⁵ and R ⁶ are identical or different and are as defined for R ³ and R ⁴ , with the proviso that R ⁵ and R ⁶ are not hydrogen,

 ═BR ¹¹ , ═AlR ¹¹ , —Ge—, —Sn—, —O—, —S—, ═SO,═SO ₂ , ═NR ¹¹ , ═CO, ═PR ¹¹ or ═P(O)R ¹¹ , where R ¹¹ , R ¹² and R ¹³ are identical or different and are a hydrogen atom, a halogen atom, a C ₁ -C ₁₀-alkyl group, a C ₁ -C ₁₀-fluoroalkyl group, a C ₆ -C ₁₀-aryl group, a C ₆ -C ₁₀-fluoroaryl group, a C ₁ -C ₁₀-alkoxy group, a C ₂ -C ₁₀-alkenyl group, a C ₇ -C ₄₀-arylalkyl group, a C ₈ -C ₄₀-arylalkenyl group or a C ₇ -C ₄₀-alkylaryl group, or R ¹¹ and R ¹² or R ¹¹ and R ¹³ , in each case with the atoms connecting them, form a ring, M ² is germanium or tin, R ⁸ and R ⁹ are identical or different and are as defined for R ¹¹ and m and n are identical or different and are zero, 1 or 2, m plus n being zero, 1 or
 2. 25. A compound of the formula I

in which M ¹ is a metal from group IVb, Vb or VIb of the Periodic Table, R ¹ and R ² are identical or different and are a hydrogen atom, a C ₁ -C ₁₀-alkyl group, a C ₁ -C ₁₀-alkoxy group, a C ₆ -C ₁₀-aryl group, a C ₆ -C ₁₀-aryloxy group, a C ₂ -C ₁₀-alkenyl group, a C ₇ -C ₄₀-arylalkyl group, a C ₇ -C ₄₀-alkylaryl group, a C ₈ -C ₄₀-arylalkenyl group or a halogen atom, R ³ and R ⁴ are identical or different and are a hydrogen atom, a halogen atom, a C ₁ -C ₁₀-alkyl group which is halogenated, a C ₆ -C ₁₀-aryl group, an —NR ₂ ¹⁰ , —SR ¹⁰ , —OSiR ₃ ¹⁰ , —SiR ₃ ¹⁰ or —PR ₂ ¹⁰ radical in which R ¹⁰ is a halogen atom, a C ₁ -C ₁₀-alkyl group or a C ₆ -C ₁₀-aryl group, R ⁵ and R ⁶ are identical or different and are a halogen atom, a C ₁ -C ₁₀-alkyl group, which is optionally halogenated, a C ₆ -C ₁₀-aryl group, an —NR ₂ ¹⁰ , —SR ¹⁰ , —OSiR ₃ ¹⁰ , —SiR ₃ ¹⁰ or —PR ₂ ¹⁰ radical in which R ¹⁰ is a halogen atom, a C ₁ -C ₁₀-alkyl group or a C ₆ -C ₁₀-aryl group, R ⁷ is

═BR ¹¹ , ═AlR ¹¹ , —Ge—, —Sn—, —O—, —S—, ═SO,═SO ₂ , ═NR ¹¹ , ═CO, ═PR ¹¹ or ═P(O)R ¹¹ , where R ¹¹ , R ¹² and R ¹³ are identical or different and are a hydrogen atom, a halogen atom, a C ₁ -C ₁₀-alkyl group, a C ₁ -C ₁₀-fluoroalkyl group, a C ₆ -C ₁₀-aryl group, a C ₆ -C ₁₀-fluoroaryl group, a C ₁ -C ₁₀-alkoxy group, a C ₂ -C ₁₀-alkenyl group, a C ₇ -C ₄₀-arylalkyl group, a C ₈ -C ₄₀-arylalkenyl group or a C ₇ -C ₄₀-alkylaryl group, or R ¹¹ and R ¹² or R ¹¹ and R ¹³ , in each case with the atoms connecting them, form a ring, M ² is silicon, germanium or tin, R ⁸ and R ⁹ are identical or different and are as defined for R ¹¹ and m and n are identical or different and are zero, 1 or 2, m plus n being zero, 1 or
 2. 26. A compound of the formula I

in which M ¹ is a metal from group IVb, Vb or VIb of the Periodic Table, R ¹ and R ² are identical or different and are a hydrogen atom, a C ₁ -C ₁₀-alkyl group, a C ₁ -C ₁₀-alkoxy group, a C ₆ -C ₁₀-aryl group, a C ₆ -C ₁₀-aryloxy group, a C ₂ -C ₁₀-alkenyl group, a C ₇ -C ₄₀-arylalkyl group, a C ₇ -C ₄₀-alkylaryl group, a C ₈ -C ₄₀-arylalkenyl group or a halogen atom, R ³ and R ⁴ are identical or different and are a hydrogen atom, a halogen atom, a C ₁ -C ₁₀-alkyl group, which is optionally halogenated, a C ₆ -C ₁₀-aryl group, an —NR ₂ ¹⁰ , —SR ¹⁰ , —OSiR ₃ ¹⁰ , —SiR ₃ ¹⁰ or —PR ₂ ¹⁰ radical in which R ¹⁰ is a halogen atom, a C ₁ -C ₁₀-alkyl group or a C ₆ -C ₁₀-aryl group, R ⁵ and R ⁶ are identical or different and are a halogen atom, a C ₁ -C ₁₀-alkyl group which is halogenated, a C ₆ -C ₁₀-aryl group, an —NR— ₂ ¹⁰ , —SR ¹⁰ , —OSiR ₃ ¹⁰ , —SiR ₃ ¹⁰ or —PR ₂ ¹⁰ radical in which R ¹⁰ is a halogen atom, a C ₁ -C ₁₀-alkyl group or a C ₆ -C ₁₀-aryl group, R ⁷ is

 ═BR ¹¹ , ═AlR ¹¹ , —Ge—, —Sn—, —O—, —S—, ═SO,═SO ₂ , ═NR ¹¹ , ═CO, ═PR ¹¹ or ═P(O)R ¹¹ , where R ¹¹ , R ¹² and R ¹³ are identical or different and are a hydrogen atom, a halogen atom, a C ₁ -C ₁₀-alkyl group, a C ₁ -C ₁₀-fluoroalkyl group, a C ₆ -C ₁₀-aryl group, a C ₆ -C ₁₀-fluoroaryl group, a C ₁ -C ₁₀-alkoxy group, a C ₂ -C ₁₀-alkenyl group, a C ₇ -C ₄₀-arylalkyl group, a C ₈ -C ₄₀-arylalkenyl group or a C ₇ -C ₄₀-alkylaryl group, or R ¹¹ or R ¹² or R ¹¹ and R ¹³ , in each case with the atoms connecting them, form a ring, M ² is silicon, germanium or tin, R ⁸ and R ⁹ are identical or different and are as defined for R ¹¹ and m and n are identical or different and are zero, 1 or 2, m plus n being zero, 1 or
 2. 27. A compound of the formula I

in which M ¹ is a metal from group IVb, Vb or VIb of the Periodic Table, R ¹ and R ² are identical or different and are a hydrogen atom, a C ₁ -C ₁₀-alkyl group, a C ₁ -C ₁₀-alkoxy group, a C ₆ -C ₁₀-aryl group, a C ₆ -C ₁₀-aryloxy group, a C ₂ -C ₁₀-alkenyl group, a C ₇ -C ₄₀-arylalkyl group, a C ₇ -C ₄₀-alkylaryl group, a C ₈ -C ₄₀-arylalkenyl group or a halogen atom, R ³ and R ⁴ are different and are a hydrogen atom, a halogen atom, a C ₁ -C ₁₀-alkyl group, which is optionally halogenated, a C ₆ -C ₁₀-aryl group, an —NR ₂ ¹⁰ , —SR ¹⁰ , —OSiR ₃ ¹⁰ , —SiR ₃ ¹⁰ or —PR ₂ ¹⁰ radical in which R ¹⁰ is a halogen atom, a C ₁ -C ₁₀-alkyl group or a C ₆ -C ₁₀-aryl group, R ⁵ and R ⁶ are identical or different and are as defined for R ³ and R ⁴ , with the proviso that R ⁵ and R ⁶ are not hydrogen, R ⁷ is

 ═BR ¹¹ , ═AlR ¹¹ , —Ge—, —Sn—, —O—, —S—, ═SO,═SO ₂ , ═NR ¹¹ , ═CO, ═PR ¹¹ or ═P(O)R ¹¹ , where R ¹¹ , R ¹² and R ¹³ are identical or different and are a hydrogen atom, a halogen atom, a C ₁ -C ₁₀-alkyl group, a C ₁ -C ₁₀-fluoroalkyl group, a C ₆ -C ₁₀-aryl group, a C ₆ -C ₁₀-fluoroaryl group, a C ₁ -C ₁₀-alkoxy group, a C ₂ -C ₁₀-alkenyl group, a C ₇ -C ₄₀-arylalkyl group, a C ₈ -C ₄₀-arylalkenyl group or a C ₇ -C ₄₀-alkylaryl group, or R ¹¹ and R ¹² or R ¹¹ and R ¹³ , in each case with the atoms connecting them, form a ring, M ² is silicon, germanium or tin, R ⁸ and R ⁹ are identical or different and are as defined for R ¹¹ and m and n are identical or different and are zero, 1 or 2, m plus n being zero, 1 or
 2. 